Properly codegen reactive attributes

packages/spacebars-compiler/compiler.js

@@ -27,6 +27,21 @@ SpacebarsCompiler._TemplateTagReplacer.def({
 
     // call super (e.g. for case where `attrs` is an array)
     return HTML.TransformingVisitor.prototype.visitAttributes.call(this, attrs);
+  },
+  visitAttribute: function (name, value, tag) {
+    var result = this.visit(value);
+    if (! this.codegen.OLDSTYLE) {
+      if (result !== value) {
+        // some template tags must have been replaced, because otherwise
+        // we try to keep things `===` when transforming.  Wrap the code
+        // in a function as per the rules.  You can't have
+        // `{id: Blaze.View(...)}` as an attributes dict because the View
+        // would be rendered more than once; you need to wrap it in a function
+        // so that it's a different View each time.
+        return BlazeTools.EmitCode(this.codegen.codeGenBlock(result));
+      }
+    }
+    return result;
   }
 });